PROJECT SUMMARY My long-term goal is to extend my research agenda regarding later-life families and well-being by incorporating innovative observational and biomarker methodologies and to develop effective family-based intervention strategies. The proposed project will provide me with training in three new areas which are critical to extend my previous training. These skills include the collection and analysis of (1) observations of family members? interactions, (2) stress, stress-protective and immune biomarkers and (3) the translation of basic research into family-based interventions. This will allow me to examine the links between family processes and biological mechanisms that influence health and well-being outcomes. This project also provides foundational knowledge which I can apply to future family-based caregiving interventions. The proposed project will highlight the role of family relations in caregivers? physical health and psychological well-being by considering the network in which caregivers are embedded. This project has three aims: (1) Determine whether perceptions of parental care preferences and perceptions of equity in the division of care influence sibling interaction strategies and identify the implications of sibling interaction strategies on sibling relationship quality, (2) identify changes in stress and stress-protective biomarkers in response to sibling interactions and (3) identify the implications of sibling relationship quality during ADRD caregiving for cumulative biological health indicators, psychological well-being and physical health. The proposed project extends this previous work by employing an innovative combination of survey, observational and biomarker data collected from two adult children in 100 families; and will be the first study to combine these three types of data to study sibling relationships in the context of caregiving. This study is novel in its approach by employing observational coding of the interaction strategies adult siblings use when discussing their parents? past and future care needs; and also assessing the physiological reactions to these interactions by measuring stress (i.e. cortisol) and stress-protective biomarkers (i.e. dehydroepiandrosterone or DHEA). Further, I will consider the consequences of sibling relationship quality on cumulative stress, stress- protective and immune (i.e. secretory immunoglobulin A (sIgA), C-reactive protein (CRP), interleukin 1-beta (IL- 1?) and herpes simplex virus-1 (HSV)) biomarkers. The findings from this study will fill a knowledge gap regarding the health vulnerability of adult children during a stressful life event. Insights from this study can help to shape future prevention and intervention efforts aimed at improving sibling interaction strategies and the overall health and well-being of adult children caring for older parents with ADRD.